When it opened four years ago, few could have foreseen the way in which a small corner of Cuba would become such a powerful symbol of America's War on Terror - and what many dislike so much about it.

Inmates from more than 40 nations are held at Guantanamo

The controversy started immediately.

Within days of their arrival, the US released pictures showing the first prisoners arriving shackled and wearing goggles.

The Pentagon realised that it had blundered and began inviting journalists to take tours.

Stage-managed

During my first visit a few weeks later, the camp still had a temporary feel.

The small wire cages were lit up through the night by arc lights and during the day by a searing sun.

Tours were carefully stage managed.

Visitors were given strict instructions not to try and communicate with detainees.

In a typically Rumsfeldian turn of phrase, the US defence secretary said the camp was the 'least worst place' to house those suspected of involvement with Al Qaeda.

By the time of a second visit, a year and a half later, a more permanent structure had emerged in the form of Camp Delta, slightly less bleak than what had come before.

Detainees had now been differentiated with some receiving better food and even the promise of possible release.

The tours had also become more slick and stage managed.

The closest we could get to a news story was the revelation that McDonald's "Happy Meals" were offered to detainees if they co-operated in interrogations.

But even then, it was hard to hide the darker side.

During a tour of the high-security wing, there was a commotion and the group was hustled away. It later emerged there had been a suicide attempt, one of many.

Justice delayed

As with so many decisions taken in the heated atmosphere after 11 September, there appears to have been relatively little thought of the long-term implications.

The site was chosen precisely because it lay outside US legal jurisdiction and the men were classified as 'enemy combatants' to deny them the rights provided to prisoners of war under the Geneva convention.

As the first detainees returned home, including to the UK, the first reports emerged of life on the inside began to trickle out, with disturbing revelations about treatment.

There was lots of talk of intelligence collection but the reality was that high-level detainees were never sent to Guantanamo, instead men like Khalid Sheikh Mohammed disappeared into the even more mysterious ghost prisons alleged to have been in Europe and elsewhere.

And whatever intelligence any foot soldiers at Guantanamo might have had would not take long to become out of date. But the problem remained - what to do with the men.

There is still no final answer.

More than 250 detainees have been transferred back to their home countries.

On arrival, some have then been set free and were agreed to have been innocently caught up in the process, others have disappeared into detention and a few have even gone back to fighting the US in Afghanistan.

About 500 prisoners remain in Guantanamo.

Some are supposed to be going through a form of military trial but even this process has been plagued by delays and legal argument.

The fourth anniversary is set to finally see the start of the first of these tribunals with a man accused of being a bodyguard to Osama bin Laden.

Torture allegations

As the first detainees returned home, including to the UK, the first reports emerged of life on the inside began to trickle out, with disturbing revelations about treatment.

Some of those who worked as interrogators also began to speak about conditions and activities that they felt went too far.

German Chancellor Angela Merkel has criticised the US over the camp

Amnesty International has marked the anniversary by releasing more allegations of what it calls torture.

As well as the alleged goings-on within the camp, the range of countries whose nationals have been held there (more than 40) - including many close allies and others whose co-operation is vital in the war on terror - has made Guantanamo a powerful symbol of discontent with US tactics in pursuing its war on terror.

At one point the plan was to slowly reduce numbers so that only a couple of hundred detainees would remain but even that appears to have slowed.